This invention relates to a process for the quaternization of polyvinyl alcohol (sometimes, hereinafter referred to as PVA) to a polymer having cationic groups. That product usually is known as cationic polyvinyl alcohol (or cationic PVA).
Two basic processes for preparing cationic PVA are known. The first is a two-step process which involves, first, copolymerization of vinyl acetate with a comonomer containing a quaternary ammonium group and, next, hydrolysis of acetate groups to hydroxyl groups. The second requires post-treatment of PVA.
Representative of the first type of PVA quaternization processes are U.S. Pat. Nos. 4,311,805 and 4,308,189 to Tohei at al., which disclose copolymerization of vinyl acetate with cationically substituted acrylamides and methacrylamides.
U.S. Pat. No. 4,109,068 to Allen teaches copolymerization of vinyl acetate with a vinyl haloacetate, which then is partially saponified and quaternized through the remaining halovinyl acetate groups.
Representative of the second type of PVA quaternization processes is Japanese Pat. No. 52-3689 to Yokkaichi, which discloses a process for post-quaternization of PVA in a slurry of acetone or other organic liquid, optionally containing water.
U.S. Pat. 4,645,794 discloses a process for the post-quaternization of PVA in an aqueous solution or an aquesous slurry, using as the quaternizing agent (chlorohydroxypropyl)trimethylammonium chloride.
Some of those processes, however, are not entirely satisfactory either because of the fact that they require expensive, not readily available starting materials, or involve multistep reactions, or result in rather low yields of the desired product, or require expensive purification methods such as dialysis.
It thus is desirable to provide a simple, inexpensive method of quaternizing PVA in satisfactory yields to a reasonably pure product which does not require difficult or expensive recovery or purification techniques.